MP2490 – 1.5A, 36V, 700KHz STEP-DOWN WITH PROGRAMMABLE OUTPUT CURRENT LIMIT

MP2490 Rev. 0.92

www.MonolithicPower.com

4

4/23/2010

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PIN FUNCTIONS

QFN10-3

Pin #

SOIC-8 /

PDIP-8

Pin#

Name

Description

1

1

VIN

Supply Voltage. The MP2490 operates from a +4.5V to +36V unregulated

power device and power supply for the whole chip.

2

2

GND

Ground. This pin is the voltage reference for the regulated output voltage.

For this reason care must be taken in its layout. This node should be placed

inducing voltage noise into the part.

3

EN

On/Off Control Input. (Only available for the MP2490DQ)

4

3

FB

Feedback. An external resistor divider from the output to GND, tapped to the

FB pin sets the output voltage. To prevent current limit run away during a

short circuit fault condition the frequency-fold-back comparator lowers the

oscillator frequency when the FB voltage is below 250mV.

5

4

SS

Connect to an external capacitor used for Soft-Start and compensation for

current limiting loop.

6

5

ISN

Negative Current Sense Input for load current limiting.

7

6

ISP

Positive Current Sense

8

PGOOD

Power good signal. When FB is less than 90% of 0.8V, PGOOD is low. It is

an open-drain output. Use a high value pull-up resistor externally to pull it up

to system power supply.

9

7

BST

Bootstrap. This capacitor is needed to drive the power switch’s gate above

the supply voltage. It is connected between SW and BST pins to form a

floating supply across the power switch driver. An on-chip regulator is used

to charge up the external boot-strap capacitor. If the on-chip regulator is not

strong enough, one optional diode can be connected from IN or OUT to

charge the external boot-strap capacitor.

10

8

SW

Switch Output. It is the source of power device.